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.\" ========================================================================
.\"
.IX Title "Xray::FluorescenceEXAFS 3pm"
.TH Xray::FluorescenceEXAFS 3pm "2022-06-28" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Ifeffit::Demeter::FluorescenceEXAFS \- Corrections for fluorescence EXAFS data
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This provides class methods for computing corrections to fluorescence
\&\s-1EXAFS\s0 data due to normalization, I0, and self-absorption effects.  The
corrections are computed from x\-ray absorption coefficients provided
by the Xray::Absorption package.
.SH "METHODS"
.IX Header "METHODS"
Note that the values returned for all methods depend on the data
resource used.  See Xray::Absorption.
.ie n .IP """mcmaster""" 4
.el .IP "\f(CWmcmaster\fR" 4
.IX Item "mcmaster"
This is called \f(CW\*(C`mcmaster\*(C'\fR for historical reasons.  It calculates the
normalization correcion for a given element.
.Sp
.Vb 1
\&  $sigma_mm = Xray::FluorescenceEXAFS\->mcmaster($element, $edge);
.Ve
.Sp
It takes the central atoms tag and the alphanumeric edge symbol as
arguments and returns the normalization correction in units of
Angstrom squared.
.Sp
\&\f(CW\*(C`normalization\*(C'\fR and \f(CW\*(C`edgestep\*(C'\fR are aliases for this method.
.ie n .IP """i0""" 4
.el .IP "\f(CWi0\fR" 4
.IX Item "i0"
This calculates the correcion due to the I0 fill gases in a
fluorescence experiment.
.Sp
.Vb 2
\&  $gases = {nitrogen=>$nitrogen, argon=>$argon, krypton=>$krypton};
\&  $sigma_i0 = Xray::FluorescenceEXAFS\->i_zero($central, $edge, $gases);
.Ve
.Sp
It takes the central atoms tag, the alphanumeric edge symbol, and a
reference to a hash containing the volume percentages of the three
gases as arguments.  It assumes that any remaining volume is filled
with helium and it correctly accounts for the fact that nitrogen is a
diatom.  It returns the I0 correction in units of Angstrom squared.
.Sp
\&\f(CW\*(C`i_zero\*(C'\fR and \f(CW\*(C`izero\*(C'\fR are aliases for this method.
.ie n .IP """self""" 4
.el .IP "\f(CWself\fR" 4
.IX Item "self"
This calculates the correcion due to self-absorption fluorescence
experiment.  It assumes that the sample is infinately thick and that
the entry and exit angles of the photons are the same.
.Sp
.Vb 2
\&  $contents = {Y=>1, Ba=>2, Cu=>3, O=>7};
\&  ($amp_i0, $sigma_i0) = Xray::FluorescenceEXAFS\->self($central, $edge, $contents);
.Ve
.Sp
It takes the central atoms tag, the alphanumeric edge symbol, and a
reference to a hash which counts the atoms in the unit cell.  It
returns a list whose zeroth element is the multiplicative amplitude
correction and whose first element is the sigma^2 correction in units
of Angstrom squared.
.Sp
\&\f(CW\*(C`overabsorption\*(C'\fR is an aliases for this method.
.SH "BUGS AND LIMITATIONS"
.IX Header "BUGS AND LIMITATIONS"
.IP "\(bu" 4
Fourth cumulant corrections are not calculated.
.IP "\(bu" 4
Geometry and thickness effects are not included in the self absorption calculation
.PP
Please report problems to Bruce Ravel (bravel \s-1AT\s0 bnl \s-1DOT\s0 gov)
.PP
Patches are welcome.
.SH "AUTHOR"
.IX Header "AUTHOR"
Bruce Ravel (bravel \s-1AT\s0 bnl \s-1DOT\s0 gov)
.PP
http://cars9.uchicago.edu/~ravel/software/
.SH "LICENCE AND COPYRIGHT"
.IX Header "LICENCE AND COPYRIGHT"
Copyright (c) 2006\-2008 Bruce Ravel (bravel \s-1AT\s0 bnl \s-1DOT\s0 gov). All rights reserved.
.PP
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See perlartistic.
.PP
This program is distributed in the hope that it will be useful,
but \s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0